1. Field of the Invention
The present invention relates to a substrate, optical fiber connecting terminal member, optical element housing member, and method of fabrication of an optical module and the substrate, and in particular to a substrate, an optical fiber connecting end member, and an optical element housing member that can connect without alignment of the cores and at high precision an optical element mounted on an optical waveguide on a substrate or mounted on the substrate to an optical fiber of an optical fiber connector that is connected to an optical fiber connecting end member or an optical element provided on an optical element housing member, and a fabrication method for an optical module and a substrate.
2. Description of the Related Art
In broadband optical communication networks and high-speed data transmission between computers, parallel optical modules and multiple core optical transmission and reception modules and the like are necessary. An increasingly higher quality and decreasing cost are required for these modules, and reducing the number of parts, simplification of the module structure, and decreased energy consumed during the fabrication process and the like are indispensable for the further improvement.
When an optical module is assembled on the device, an ordinary pigtail module entails the problem of processing of the optical fiber's excess length, which means that extra space is necessary in order to accommodate the optical fiber mounted in the optical module. Therefore, using an optical module with an attached optical fiber receptacle that can be detached from the optical fiber is desired.
In order to apply the multiple core optical fiber receptacle structure to this optical module, it is necessary to align with high precision the relative positions of a guide pin or a guide pin insertion hole, which are used to connect to the multiple core optical fiber connector, and the optical axis of the optical module.
Active alignment, for example, can be considered to be such a core alignment method. In this alignment method, positions are adjusted by moving the optical module and the receptacle relative to each other while the optical module is emitting light, so that the light is most strongly incident on the optical fiber. Then this receptacle is attached to the optical module.
However, in this active alignment, because the position adjustment of the optical module and the receptacle must be carried out using a precision manual operation, the optical module becomes a factor that causes a high cost. In order to decrease the cost of the optical module, this kind of alignment by a precision manual operation should be avoided, and an optical module having a structure that can be assembled without core alignment is required.
FIG. 15 is an exploded perspective view showing the optical waveguide part disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 8-248269, which is one example of a multiple core optical module having a structure whose assembly does not require core alignment, and FIG. 16 is a partial cross-sectional perspective view of the same. In this optical waveguide path, both ends 100a and 100b of an optical waveguide body 100 are respectively inserted into and fixed in separate connecting end members 101 and 101.
The optical waveguide body 100 provides a substrate 102, a cladding 103, and an optical waveguide core 104 comprising a plurality of cores 104a. On the upper surface of the cladding 103, two V-shaped grooves 105a and 105b are formed on respective sides of the optical waveguide core 104.
On the connecting terminal member 101, a through hole 107 and guide pin insertion holes 108a and 108b that pass from the one end surface 106a thereof to the other end surface 106b thereof are formed, and in the through hole 107, V-shaped projections 109a and 109b that engage the V-shaped grooves 105a and 105b are formed.
In this optical waveguide part, the one end 100a of the optical waveguide body 100 is inserted into the through hole 107 of the connecting end member 101 such that the V-shaped grooves 105a and 105b thereof are engaged with the V-shaped projections 109a and 109b. The end surface of each core 104a of the light guiding core 104 and the end surface 106a of the connecting end member 101 are made flush to each other, and while being held in this state, both are attached and fixed, and thereby the optical waveguide body 100 can be fixed to the connecting end member 101 without core alignment.
However, in this optical waveguide part, because the optical waveguide body 100 is inserted into the connecting end member 101 while the V-shaped grooves 105a and 105b are engaged in the V-shaped projections 109a and 109b, there is the problem that the V-shaped grooves 105a and 105b and the V-shaped projections 109a and 109b can be easily broken.
Thus, an optical waveguide that avoids this problem is disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 8-248269.
As is shown in FIG. 17, this optical waveguide part is structured so that substantially identically shaped V-shaped grooves 111a and 111b are formed at positions in the through hole 107 of the connecting end member 101 opposite to the V-shaped grooves 105a and 105b of the optical waveguide body 100, and the respective optical fibers 112 and the like are interposed between the V-shaped grooves 105a and 111a and between the V-shaped grooves 105b and 111b. 
In addition, the optical waveguide apparatus disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 9-105838, is another example that avoids the problem described above.
As is shown in FIG. 18, in this optical waveguide apparatus, the connecting end members 202 and 203, which surround and engage both side surfaces and the upper surface 210 of the waveguide chip 201 by the engaging recess 216, engage and fasten the connecting end surfaces 225a and 225b of the waveguide chip 201 that forms the core 206 and the clad 205 on the substrate 210, to form the optical waveguide apparatus shown in FIG. 19.
In this optical waveguide apparatus, both end sides of the optical fiber 209 are sandwiched between the V-shaped grooves 208a and 208b formed on both sides of the upper surface 210 of the waveguide chip 201 and the inverse V-shaped grooves 214 and 215 formed at positions corresponding to the V-shaped grooves 208a and 208b of the engagement recess 216 of the connecting end members 202 and 203, and thereby the positioning of the waveguide chip 210 and the connecting end members 202 and 203 is carried out.
However, in the conventional optical waveguide part and the optical waveguide apparatus described above, an optical fiber, which is a very small part, must be aligned with and mounted on a V-shaped groove and an inverse V-shaped groove, and there is the problem that obtaining high precision is difficult.
In addition, the problem with the optical waveguide part and optical waveguide apparatus is the precision of the V-shaped grooves. Thus, a method that improves the precision of the V-shaped groove is disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 9-105838.
This method includes a method of forming a V-shaped groove using machine processing and a method of forming a rectangular groove by etching processing, but generally, in these methods, achieving sub-micron level precision is difficult, and applying these methods to single mode optical fiber arrays presents problems.